1. Technical Field
The present invention relates to a display element, an image display system, and a method of controlling the display element.
2. Related Art
In the past, there has been known a technology of displaying a picture on a screen using a projector or the like. In recent years, there has been proposed a technology of diffusing or scattering a picture light in a transparent screen to thereby display the picture therein. By using the technology, figures and objects in the real space where the screen is disposed are observed through the screen to thereby make it possible to assimilate the picture with the real space.
For example, by projecting the information, which is related to the articles displayed in the window, on the window glass, it is possible to efficiently display the information without hindering observation of the articles on display. In the windows of a bank or the like, by displaying the visitor's information on the receptionist side, or displaying the receptionist's information on the visitor side, it becomes possible to proceed with the office counter work smoothly. In videoconferences, unmanned receptions, and so on, by projecting a picture only with a clipped figure, it is possible to provide reality as if the figure were present.
As described above, by using a transparent screen, it is possible to provide a picture representation without making the observer appreciate presence of the display as a device, and thus, it becomes possible to perform efficient information provision and picture rendering with a sense of presence. As the transparent screen, those disclosed in JP-A-2000-75139 (Document 1) and JP-A-6-82748 (Document 2) can be cited. In Document 1, there is proposed a method of manufacturing a hologram screen for recording a pattern due to the interference between a reference light as a non-diffused light and an object light diffused by a light diffusing body. Document 2 proposes a screen capable of switching between transmission and diffusion using a liquid crystal layer.
An Internet website “light control mirror” by Advanced Industrial Science and Technology (AIST), Internet URL: http://www.aist.go.jp/aist_j/press_release/pr2007/pr20071121/pr20071121.html, (Document 3) discloses a light control mirror film made of an electrochromic material varied between a mirror state and a transparent state by controlling the applied voltage.
Incidentally, the screens using the technologies of Documents 1 and 2 are transparent in a nonuse state, and therefore make it possible to provide video equipment decreasing the presence of the screen itself in the nonuse state as much as possible and being in harmony with the surrounding environment. However, the scattering characteristics of the screens include mainly forward scattering and only little backward scattering. In other words, in the case of using the screens as a screen for a projection type projector, it is possible to project a sufficiently visible picture as a rear projection screen. However, in the case of using the screens as a front projection screen, scattering is insufficient, and therefore, the projector fails to project the sufficiently visible picture on the screen.
Therefore, there has been demanded a screen for the front projection type projector capable of decreasing the presence of the screen in the nonuse state, and providing sufficient scattering characteristics in the use state. Further, in order to realize such a screen, there have been requested a display element for controlling diffusion and transmission of light, and a method of controlling the display element.